A motor control apparatus generates a control signal for causing a switching element included in an inverter to perform an ON/OFF operation. The switching element performs the ON/OFF operation according to the control signal output from the motor control apparatus, whereby the inverter converts output power of a direct-current power supply into alternating-current power and supplies the alternating-current power to a motor. Consequently, the motor is controlled to have desired values as the position and the speed or the torque thereof. As this type of the motor, an induction motor, a permanent magnet synchronous motor, or the like is used.
As examples of the direct-current power supply of the inverter, there are, for example, a diode converter that rectifies electric power output from a three-phase alternating-current power supply and outputs the rectified electric power and a DC/DC converter that subjects electric power output from a battery or a capacitor to voltage level conversion and outputs the electric power.
This kind of the direct-current power supply generally has upper limits in electric power and a voltage that the direct-current power supply can output. The direct-current power supply needs to be used within ranges of the upper limits. For example, an upper limit of electric power that the battery or the capacitor can output depends on the life, accumulated energy, and the like of the battery or the capacitor. In the DC/DC converter or the diode converter, specifications of a voltage value, a current value, and the like that can the DC/DC converter or the diode converter can handle are equivalent to the upper limit of the electric power. Further, in the diode converter, there is a power supply facility capacity of a three-phase alternating-current power supply as another limiting factor. Therefore, electric power that the inverter can output is also limited. As the limitation, although there is a limitation due to the specifications of the inverter itself, there is a limitation that alternating-current power to be output should be set to be equal to or smaller than output power of the direct-current power supply.
The inverter supplies the direct-current voltage of the direct-current power supply to the motor via an ON/OFF operation of a semiconductor switching element. Therefore, a voltage exceeding the direct-current voltage output from the direct-current power supply cannot be supplied to the motor. Therefore, like the electric power explained above, a voltage that the inverter can output is also limited. Because of the reasons explained above, the motor control apparatus needs to control the motor within limitation ranges of the electric power and the voltage that depend on the direct-current power supply and the inverter specifications.
To solve the problems, for example, Patent Literature 1 discloses a technology for generating, taking into account operation timing of a motor and supply power of a power supply in advance, a position command that assumes limitations on acceleration (torque) and motor speed of the motor. When this technology is used, it is possible to suppress electric power necessary for acceleration and deceleration of the motor to be within a predetermined range.